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1/* mpi-add.c - MPI functions
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation, Inc.
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Note: This code is heavily based on the GNU MP Library.
8 * Actually it's the same code with only minor changes in the
9 * way the data is stored; this is to support the abstraction
10 * of an optional secure memory allocation which may be used
11 * to avoid revealing of sensitive data due to paging etc.
12 */
13
14#include "mpi-internal.h"
15
16int mpi_add(MPI w, MPI u, MPI v)
17{
18 mpi_ptr_t wp, up, vp;
19 mpi_size_t usize, vsize, wsize;
20 int usign, vsign, wsign;
21 int err;
22
23 if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
24 usize = v->nlimbs;
25 usign = v->sign;
26 vsize = u->nlimbs;
27 vsign = u->sign;
28 wsize = usize + 1;
29 err = RESIZE_IF_NEEDED(w, wsize);
30 if (err)
31 return err;
32 /* These must be after realloc (u or v may be the same as w). */
33 up = v->d;
34 vp = u->d;
35 } else {
36 usize = u->nlimbs;
37 usign = u->sign;
38 vsize = v->nlimbs;
39 vsign = v->sign;
40 wsize = usize + 1;
41 err = RESIZE_IF_NEEDED(w, wsize);
42 if (err)
43 return err;
44 /* These must be after realloc (u or v may be the same as w). */
45 up = u->d;
46 vp = v->d;
47 }
48 wp = w->d;
49 wsign = 0;
50
51 if (!vsize) { /* simple */
52 MPN_COPY(wp, up, usize);
53 wsize = usize;
54 wsign = usign;
55 } else if (usign != vsign) { /* different sign */
56 /* This test is right since USIZE >= VSIZE */
57 if (usize != vsize) {
58 mpihelp_sub(wp, up, usize, vp, vsize);
59 wsize = usize;
60 MPN_NORMALIZE(wp, wsize);
61 wsign = usign;
62 } else if (mpihelp_cmp(up, vp, usize) < 0) {
63 mpihelp_sub_n(wp, vp, up, usize);
64 wsize = usize;
65 MPN_NORMALIZE(wp, wsize);
66 if (!usign)
67 wsign = 1;
68 } else {
69 mpihelp_sub_n(wp, up, vp, usize);
70 wsize = usize;
71 MPN_NORMALIZE(wp, wsize);
72 if (usign)
73 wsign = 1;
74 }
75 } else { /* U and V have same sign. Add them. */
76 mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
77 wp[usize] = cy;
78 wsize = usize + cy;
79 if (usign)
80 wsign = 1;
81 }
82
83 w->nlimbs = wsize;
84 w->sign = wsign;
85 return 0;
86}
87EXPORT_SYMBOL_GPL(mpi_add);
88
89int mpi_sub(MPI w, MPI u, MPI v)
90{
91 int err;
92 MPI vv;
93
94 vv = mpi_copy(v);
95 if (!vv)
96 return -ENOMEM;
97
98 vv->sign = !vv->sign;
99 err = mpi_add(w, u, vv);
100 mpi_free(vv);
101
102 return err;
103}
104EXPORT_SYMBOL_GPL(mpi_sub);
105
106int mpi_addm(MPI w, MPI u, MPI v, MPI m)
107{
108 return mpi_add(w, u, v) ?:
109 mpi_mod(w, w, m);
110}
111EXPORT_SYMBOL_GPL(mpi_addm);
112
113int mpi_subm(MPI w, MPI u, MPI v, MPI m)
114{
115 return mpi_sub(w, u, v) ?:
116 mpi_mod(w, w, m);
117}
118EXPORT_SYMBOL_GPL(mpi_subm);
1/* mpi-add.c - MPI functions
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation, Inc.
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Note: This code is heavily based on the GNU MP Library.
8 * Actually it's the same code with only minor changes in the
9 * way the data is stored; this is to support the abstraction
10 * of an optional secure memory allocation which may be used
11 * to avoid revealing of sensitive data due to paging etc.
12 */
13
14#include "mpi-internal.h"
15
16/****************
17 * Add the unsigned integer V to the mpi-integer U and store the
18 * result in W. U and V may be the same.
19 */
20void mpi_add_ui(MPI w, MPI u, unsigned long v)
21{
22 mpi_ptr_t wp, up;
23 mpi_size_t usize, wsize;
24 int usign, wsign;
25
26 usize = u->nlimbs;
27 usign = u->sign;
28 wsign = 0;
29
30 /* If not space for W (and possible carry), increase space. */
31 wsize = usize + 1;
32 if (w->alloced < wsize)
33 mpi_resize(w, wsize);
34
35 /* These must be after realloc (U may be the same as W). */
36 up = u->d;
37 wp = w->d;
38
39 if (!usize) { /* simple */
40 wp[0] = v;
41 wsize = v ? 1:0;
42 } else if (!usign) { /* mpi is not negative */
43 mpi_limb_t cy;
44 cy = mpihelp_add_1(wp, up, usize, v);
45 wp[usize] = cy;
46 wsize = usize + cy;
47 } else {
48 /* The signs are different. Need exact comparison to determine
49 * which operand to subtract from which.
50 */
51 if (usize == 1 && up[0] < v) {
52 wp[0] = v - up[0];
53 wsize = 1;
54 } else {
55 mpihelp_sub_1(wp, up, usize, v);
56 /* Size can decrease with at most one limb. */
57 wsize = usize - (wp[usize-1] == 0);
58 wsign = 1;
59 }
60 }
61
62 w->nlimbs = wsize;
63 w->sign = wsign;
64}
65
66
67void mpi_add(MPI w, MPI u, MPI v)
68{
69 mpi_ptr_t wp, up, vp;
70 mpi_size_t usize, vsize, wsize;
71 int usign, vsign, wsign;
72
73 if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
74 usize = v->nlimbs;
75 usign = v->sign;
76 vsize = u->nlimbs;
77 vsign = u->sign;
78 wsize = usize + 1;
79 RESIZE_IF_NEEDED(w, wsize);
80 /* These must be after realloc (u or v may be the same as w). */
81 up = v->d;
82 vp = u->d;
83 } else {
84 usize = u->nlimbs;
85 usign = u->sign;
86 vsize = v->nlimbs;
87 vsign = v->sign;
88 wsize = usize + 1;
89 RESIZE_IF_NEEDED(w, wsize);
90 /* These must be after realloc (u or v may be the same as w). */
91 up = u->d;
92 vp = v->d;
93 }
94 wp = w->d;
95 wsign = 0;
96
97 if (!vsize) { /* simple */
98 MPN_COPY(wp, up, usize);
99 wsize = usize;
100 wsign = usign;
101 } else if (usign != vsign) { /* different sign */
102 /* This test is right since USIZE >= VSIZE */
103 if (usize != vsize) {
104 mpihelp_sub(wp, up, usize, vp, vsize);
105 wsize = usize;
106 MPN_NORMALIZE(wp, wsize);
107 wsign = usign;
108 } else if (mpihelp_cmp(up, vp, usize) < 0) {
109 mpihelp_sub_n(wp, vp, up, usize);
110 wsize = usize;
111 MPN_NORMALIZE(wp, wsize);
112 if (!usign)
113 wsign = 1;
114 } else {
115 mpihelp_sub_n(wp, up, vp, usize);
116 wsize = usize;
117 MPN_NORMALIZE(wp, wsize);
118 if (usign)
119 wsign = 1;
120 }
121 } else { /* U and V have same sign. Add them. */
122 mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
123 wp[usize] = cy;
124 wsize = usize + cy;
125 if (usign)
126 wsign = 1;
127 }
128
129 w->nlimbs = wsize;
130 w->sign = wsign;
131}
132EXPORT_SYMBOL_GPL(mpi_add);
133
134void mpi_sub(MPI w, MPI u, MPI v)
135{
136 MPI vv = mpi_copy(v);
137 vv->sign = !vv->sign;
138 mpi_add(w, u, vv);
139 mpi_free(vv);
140}
141EXPORT_SYMBOL_GPL(mpi_sub);
142
143void mpi_addm(MPI w, MPI u, MPI v, MPI m)
144{
145 mpi_add(w, u, v);
146 mpi_mod(w, w, m);
147}
148EXPORT_SYMBOL_GPL(mpi_addm);
149
150void mpi_subm(MPI w, MPI u, MPI v, MPI m)
151{
152 mpi_sub(w, u, v);
153 mpi_mod(w, w, m);
154}
155EXPORT_SYMBOL_GPL(mpi_subm);